In vehicle wiper devices that wipe the glass of a windshield or the like in an automobile, a wiper motor moves a wiper blade with an attached wiper arm back and forth between a lower return position and an upper return position. The movement of the wiper arm most often forms a substantially circular arc shaped trajectory centered on a pivot shaft of the wiper arm. A wiping range, this being a region where the windshield glass or the like is wiped by the wiper blade, accordingly has a fan-like shape centered on the pivot shaft.
In vehicle wiper devices, it is necessary to prioritize wiping of the windshield glass on the side of a driver's seat in order to secure the driver's field of view. Moreover, the windshield glass of an automobile is substantially in the shape of an isosceles trapezoid. Therefore, in parallel (tandem) wiper devices in which two wiper arms swing at the same time and in the same direction as each other, in cases in which the pivot shafts are provided below the windshield glass, an upper return position of the wiper blade on the driver's seat side is provided at a position alongside and close to a driver's seat side edge of the isosceles trapezoid shaped windshield glass (one upright side of the isosceles trapezoid shape).
In order to prioritize wiping of the driver's seat side of the windshield glass, in a tandem wiper device, the upper return position of the wiper blade on the front passenger seat side is also provided alongside the driver's seat side edge of the windshield glass. However, as described above, since the wiping ranges of the wiper blades are substantially fan shaped, providing the upper return positions at the positions described above results in a region that is not wiped, centered on an upper corner on the front passenger seat side of the windshield glass.
Japanese Patent Application Laid-Open (JP-A) No. 2000-25578 discloses a wiper device that employs a four-piece link mechanism as a link mechanism of the wiper device. The four-piece link mechanism changes the position of a wiping range on a front passenger seat side of windshield glass by moving a wiper arm into the non-wiped region described above while the wiper arm is in operation.
As illustrated in FIG. 15, the wiper device described in JP-A No. 2000-25578 transmits drive force of a motor through a four-piece link mechanism 160 to a front passenger seat side wiper arm 150P, such that a front passenger seat side wiper blade 154P wipes a wiping range Z12 between a lower return position P4P and an upper return position P3P. In FIG. 15, the wiping range Z10 would be the wiping range of the wiper arm moving about the pivot shaft if the wiper device did not include the four-piece link mechanism 160. As illustrated in FIG. 15, the wiper device described in JP-A No. 2000-25578 is capable of wiping up to an area closer to an upper corner on the front passenger seat side of a windshield glass 1 than a wiper device that does not include the four-piece link mechanism 160.